1. Field of the Invention
This invention relates to novel liquid-crystalline substances and liquid crystal compositions containing the same, and more particularly it relates to chiral liquid-crystalline substances having an optically active alkyl group and chiral liquid crystal compositions containing the same.
2. Description of the Prior Art
For liquid crystal display elements, the TN (Twisted Nematic) type display mode has currently been most widely employed. This mode, however, has a drawback that the response rate is late. In this respect, various improvements have been attempted, but a possibility of its improvement to a large extent does not appear to be expected so much. As one of the substitutive modes therefor, there is a mode utilizing a ferroelectric liquid crystal (N. A. Clark et al: Applied Phys. lett., 36, 899 (1980)). This mode utilizes the chiral smectic C phase (hereinafter abbreviated to SC* phase) or the chiral smectic H phase (SH* phase) of ferroelectric liquid crystals, and those having these phases in the vicinity of room temperature are preferable. Certain compounds used for such a purpose have been known, but there is a practical problem in respect of safety, etc. Mainly in order to develop liquid crystal substances suitable to be utilized for this display mode, the present inventors have made extensive research for liquid crystal substances containing an optically active group.